Knowledge Bank

Rotational spectrum of the CoCO radical generated by ultraviolet photolysis of $Co(CO)3NO$ was measured in the millimeter wave region to determine rotational and hyperfine interaction constants. Rotational transitions ranging from J = 29.5 - 28.5 to 34.5 - 33.5 were assigned in the $\Omega =3/2$ and $\Omega =5/2$ spin substates of the $X2\Delta i$ ground vibronic state as well as in the vibrationally excited states $\nu 2,\nu 3$, and $2\nu 2$ of the $\Omega =5/2$ spin substate. Each rotational transition was split into 8 hyperfine components due to the $\mathrm{<mrow\; data-mjx-texclass="ORD">59</mrow>}Co$ nucleus. Molecular constants, including the rotational constant B, centrifugal distortion constant D, nuclear spin-orbit interaction constant a, Fermi contact interaction constant $bF$, magnetic dipolar interaction constant c, and nuclear quadrupole interaction constant eQq, were determined for the vibrationally ground state by least squares fitting of the observed spectrum. The equilibrium rotational constant $Be$ was determined to be 4435.7510(18) MHz and the internuclear distance between Co and C was evaluated to be $1.688\backslash AA$. The a and c values are consistent with the values estimated from the hyperfine constants of the $\mathrm{<mrow\; data-mjx-texclass="ORD">59</mrow>}Co$ atom. The $bF$ value is nearly equal to zero.